U.S. patent number 5,408,523 [Application Number 07/901,737] was granted by the patent office on 1995-04-18 for electronic remote data recorder with facsimile output for utility ac power systems.
This patent grant is currently assigned to Basic Measuring Instruments, Inc.. Invention is credited to Erich W. Gunther, Alexander McEachern, Jamie Nicholson, Scott C. Terry.
United States Patent |
5,408,523 |
McEachern , et al. |
April 18, 1995 |
Electronic remote data recorder with facsimile output for utility
AC power systems
Abstract
A stand-alone electronic measuring instrument for measuring AC
(alternate current) power parameters on a utility distribution
system wherein the measurement results are communicated
telephonically to a facsimile device. Well-known techniques are
used to acquire and accumulate analog signals representative of
voltages and currents on an AC power system and digital signals. If
the signals exceed a programmed threshold, or if an interval of
time elapses, or if some other triggering even occurs, the
instrument prepares a bit-mapped digital report on its accumulated
input signals which may contain text, graphics, or both. The
instrument then employs well-known techniques to telephonically
transmit this report directly to a facsimile receiver without
employing an intervening computer system.
Inventors: |
McEachern; Alexander (Oakland,
CA), Terry; Scott C. (Pleasanton, CA), Nicholson;
Jamie (Foster City, CA), Gunther; Erich W. (Knoxville,
TN) |
Assignee: |
Basic Measuring Instruments,
Inc. (Santa Clara, CA)
|
Family
ID: |
25414728 |
Appl.
No.: |
07/901,737 |
Filed: |
June 22, 1992 |
Current U.S.
Class: |
379/106.03;
340/870.02; 358/442 |
Current CPC
Class: |
H04M
11/04 (20130101) |
Current International
Class: |
H04M
11/04 (20060101); H04M 011/00 () |
Field of
Search: |
;379/100,106,107,102,104,105,97,98,92,93 ;340/870.02
;358/442,400,401 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Damar System Report" SYGNUS Controls, Inc. Jan. 26, 1990..
|
Primary Examiner: Kuntz; Curtis
Assistant Examiner: Woo; Stella L.
Attorney, Agent or Firm: Haverstock, Medlen &
Carroll
Claims
We claim:
1. An electronic remote data recorder with facsimile output for
utility AC power systems comprising:
a. a first analog measuring apparatus coupled to an AC power line
for measuring voltage and current signals through the power
line;
b. a first isolation circuit coupled to the AC power line for
isolating appropriate voltage levels from the voltage signal;
c. a scaling circuit coupled to the first isolation circuit for
scaling the signals;
d. a first filtering circuit coupled to the scaling circuit for
filtering unwanted frequencies out of the signals and forming a
filtered signal;
e. an integrating circuit coupled to the first filtering circuit
for integrating the filtered signal over time;
f. a multiplexing circuit coupled to the first isolation circuit,
the scaling circuit, the first filtering circuit and the
integrating circuit for multiplexing the signals;
g. an analog-to-digital converter coupled to the multiplexing
circuit for converting the signals from analog to digital thereby
forming digital signals representing the signals;
h. a second digital measuring apparatus coupled to switch contacts
on the power line for measuring digital signals from the switch
contacts;
i. a second isolation circuit coupled to the second digital
measuring apparatus for isolating appropriate voltages from the
digital signals;
j. a second filtering circuit coupled to the second isolation
circuit for filtering out frequencies not of interest from the
digital signals;
k. a level shifting circuit coupled to the second filtering circuit
for shifting the level of the digital signals to an appropriate
level;
l. a digital multiplexer coupled to the second isolation circuit,
the second filtering circuit and the level shifting circuit for
multiplexing the digital signals;
m. a first microprocessor coupled to the analog-to-digital
converter and the digital multiplexer;
n. a first RAM coupled to the first microprocessor for storing
system data and accumulated measurement data;
o. a first ROM coupled to the first microprocessor for storing data
and instructions used by the first microprocessor;
p. a real-time clock and calendar coupled to the first
microprocessor for keeping the current time and date accessible by
the first microprocessor;
q. a second microprocessor coupled to the first microprocessor, the
first RAM and the real-time clock and calendar for issuing a report
of the accumulated measurement data when triggered by the first
microprocessor;
r. a second RAM coupled to the second microprocessor for storing
setup and system data and a format for the report;
s. a second ROM coupled to the second microprocessor for storing
data and instructions used by the second microprocessor; and
t. a facsimile modem coupled to the second microprocessor for
communicating with other remote systems for receiving the setup
data and for transmitting the accumulated measurement data to a
remote system periodically or upon a trigger condition.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic measuring apparatus. More
specifically, this invention relates to a stand-alone electronic
measuring apparatus for utility AC power systems incorporating
analog voltage and current inputs, digital inputs, trigger event
processing, and coupling to telephonic facsimile apparatus without
an intervening computer system.
2. Background of the Invention
It is often necessary to read the results of an instrument on a
utility power distribution system at some distance from where it is
located. For example, the power flow through a particular
transformer may be read by an operator at an office miles away, or
the power factor of a branch circuit leaving a substation may be
checked electronically without physically visiting the substation.
Early remote instruments were connected to their output devices by
direct cables. More recent instruments may employ communication
techniques such as power line carrier, radio transmission, or the
telephone switching network to transmit their readings.
If an instrument is read frequently enough, it may be appropriate
to install a remote output device that is dedicated to the
instrument. But if the information from the instrument is required
infrequently, it is common practice to employ an output device,
typically a computer, that can be shared between several
instruments. For example, a single personal computer can easily be
employed to occasionally interrogate and report on the status of
several power quality instruments on a single power distribution
network. This approach works well with many kinds of
measurements.
However, if the instruments are a trigger-type instruments (that
is, they are instruments that need to report their data at
unpredictable intervals) with limited ability to store the
measurements, a remote output device, typically a personal
computer, must be standing by at all times to receive the
measurements, or data may be lost. For example, if the instrument
is an AC power system lightning strike recorder with sufficient
storage space for data about a single lightning strike, and it
records a strike, it must either be able to communicate its
measurements to its remote output device before it detects a second
lightning strike or lose its data about subsequent lightning
strikes.
At utility companies, it is often difficult to economically justify
dedicating a personal computer to standby communications from
instruments, especially if the communication are infrequent. Even
when a personal computer can be justified, it is often difficult to
economically justify the associated outside telephone line required
for that computer.
In some systems, such as the one disclosed by French et al. in U.S.
Pat. No. 5,061,916, the output of remote instruments in a building
automation system are coupled to a central control computer which
in turn generates and transmits a report to a standard facsimile
apparatus. This approach succeeds in remotely presenting the data
collected by the instruments, but does not succeed in eliminating
the requirement to dedicate a personal computer and its associated
communication network to standby communications from
instruments.
When making remote AC power system measurements, it is often
necessary to check the measured data at an arbitrary time. For
example, a utility company may receive an urgent telephone call
from a customer requesting information about power line
disturbances that have taken place in the last fifteen minutes. In
situations like this, the user of a remote AC power measurement
system may need to request that the remote sensor provide a report
immediately, whether or not any triggering event has occurred.
The French reference does not disclose any method for instructing
their building automation system to generate a report in response
to a request signal.
The present invention solves the problem of requiring a standby
computer by coupling the output of a remote AC power instrument
directly to a facsimile apparatus via the telephone system without
an intervening computer.
The present invention solves the problem of generating a report in
response to a request signal by instructing the remote instrument
to generate and transmit a report whenever it receives a phone
communication that it cannot otherwise process, thus allowing a
user to trigger a report by simply telephoning the instrument,
waiting for it to answer, then hanging up.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a block diagram of an embodiment of the invention.
FIG. 2 shows the top left corner of a bit-mapped report prepared by
the invention.
FIG. 3 shows the invention operating in conjunction with a
facsimile apparatus.
FIGS. 4 and 5 show flow diagrams of algorithms executed by the
microprocessors in the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Beginning at the far left of FIG. 1, analog signals from utility
distribution-system voltage and current sensors 1 are applied to
isolation, scaling, filtering, integrating and multiplexing
circuits 2 that employ any well-known techniques to isolate
appropriate voltage levels, scale the signals to an appropriate
level for further processing, filter out frequencies that are not
of interest, integrate the resulting signal over time, and present
appropriately multiplexed signals to an Analog to Digital converter
3. Digital signals from switch contacts such as power system
protective relays and the like 4 are applied to isolating,
filtering, and level shifting circuits 5 that employ any well-known
techniques to isolate appropriate voltage levels, filter out
frequencies that are not of interest, shift voltage logic to an
appropriate level, and present the logic signals to a digital
multiplexed 6. The outputs of the Analog to Digital converter 3 and
the digital multiplexed 6 are applied to a first microprocessor
7.
The first microprocessor 7 employs a first read-only memory (ROM)
8, a first random-access memory (RAM) 10, and a real-time
clock/calendar 9 to execute an algorithm shown in FIG. 4. This
algorithm has two outputs: accumulated power parameter measurement
data stored in the first RAM 10, and detection of a trigger even
which activates a bidirectional signal line 11 connected to a
second microprocessor 12.
The first RAM 10 contains system data such as stacks and pointers,
setup data such as thresholds and scaling factors, and accumulated
measurement data.
The second microprocessor 12 employs the second ROM 13, the second
RAM 14, and the real-time clock/calendar 9 to execute an algorithm
shown in FIG. 5.
The second RAM 14 contains system data such as stacks and pointers,
setup data such as telephone numbers and facsimile header
information, and space for a bit-mapped image of a report such as
the one shown in FIG. 2, or a portion thereof.
When the second microprocessor 12 either detects or creates a
trigger event on the bidirectional signal line 11, the algorithm in
FIG. 5 causes a pixel-by-pixel bit-map of a report to be created in
the second RAM 14. This report is based on data accumulated by the
first microprocessor 7 in the first RAM 10. Once a bit-map of the
report, or a portion thereof, is stored in the second RAM 14, the
second microprocessor causes the facsimile modem 15 to employ any
well-known technique to cause the bit-map report stored in the
second RAM 14 to be transmitted through a telephone connection 16
to a standard facsimile receiver which then prints the report.
The second microprocessor 12 is also capable of receiving set-up
data from a controlling computer through the facsimile modem 15.
This setup data, stored in the second RAM 14, includes thresholds,
the telephone number of the facsimile apparatus which is designated
to receive reports from this instrument, and header information for
the facsimile reports prepared by this instrument such as the name
and office location of the individual to whom the report is to be
sent.
The second microprocessor 12 is also capable of initiating a
trigger event whenever it receives a phone call that it cannot
otherwise process. This permits the user of the instrument to
request a facsimile report simply by dialing the telephone number
of the instrument.
A power supply 17 employs well-known techniques to provide power to
the microprocessor-based system. It includes long-term battery
support for the real-time clock/calendar 9 and the data in the
first RAM 10 and second RAM 14, and short-term battery support for
the entire instrument so that it can communicate during power
failures.
Turning now to FIG. 2, we see the top left corner of a typical
pixel-by-pixel bit-map of a report prepared by the second
microprocessor 12 and stored in the second RAM 14. Each byte of
memory 20, 21, 22 contains eight bits in which a "zero" corresponds
to white and a "one" corresponds to black. Each pixel row 23 of the
report consists of 256 bytes which may contain black pixels and
white pixels 24. The pixels are set in such a way that the sequence
of pixel rows 23 form letters, numbers, and punctuation marks or
form graphic elements such as lines, shaded areas, and charts. The
pixels in FIG. 2 show the word "REPORT" and the upper portion of a
graphic data presentation.
Turning now to FIG. 3, we see an overview of the instrument in
operation. The instrument 34 receives input signals from voltage
and current sensors and contacts on cable 30. A printed wiring
board 32 contains the two microprocessors 7, 12 of FIG. 1 and all
their associated circuitry. The facsimile modem 15 of FIG. 1 is
contained on a separate printed wiring board 33, and connects
through cable 35 to the telephone system 36. Signals sent by
facsimile modem 33 through the cable 35 to the telephone system 36
are received and printed by a standard facsimile receiver 38.
Turning now to FIG. 4, we see a flow diagram of the algorithm
executed by the first microprocessor 7 of FIG. 1. The algorithm
enters a loop at START 40. In block 41 it acquires the values of
all of the analog inputs from sensors 1, and it acquires all of the
digital values from switch contacts or other systems 4, and it
acquires the time and date of this set of samples from the
real-time clock/calendar 9. Block 42 stores the values that were
acquired in Block 41 in the Accumulated Data RAM 10. Block 43
inspects the analog values and compares them with thresholds stored
in the set-up data. If any of the values exceed a threshold, the
algorithm jumps to Block 49 and activates the trigger line 11. If
not, the algorithm proceeds to block 44. In Block 44, using
instructions from the set-up data and values from Block 41, the
algorithm calculates certain calculated power parameter values. For
example, the set-up data might contain instructions to multiply an
input from an analog voltage sensor by an input from an analog
current sensor to form a calculated watts value, and it might
contain instructions to double this watts value if a certain
digital switch input is closed; this watts value may be
representative of the power consumption at the measuring site.
Block 44 stores these calculated values in the Accumulated Data RAM
10. Block 46 inspects these calculated values and compares them to
thresholds in the set-up data. If any of these values exceed a
threshold, the algorithm jumps to Block 49 and activates the
trigger line 11. Block 47 inspects the digital input values, and,
using instructions from the set-up data, determines if there have
been any changes in critical digital values. If critical digital
values have changed, the algorithm jumps to Block 49 and activates
the trigger line 11. Block 47 may logically combine various digital
values according to instructions in the set-up data. Block 48 sets
the timing of the loop execution by inserting a delay. For example,
if the delay in Block 48 is set to one minute minus the execution
times of Blocks 41 through 47, a new set of samples will be
acquired once per minute.
Alternated embodiments of the invention may employ more
sophisticated interrupt-driven timing algorithms. Alternate
embodiments of the invention may employ more sophisticated
calculations in Block 45, including Fourier Transforms, Root Mean
Square, and minimum-average-maximum calculations. Calculations may
incorporate the values of previous samples as well as present
sample values. Alternate embodiments may include circuits or
algorithms to extract particular signals from the AC power system,
including such disturbances as impulses, waveshape faults, high
frequency noise, frequency variations, power failures, and the
like.
Turning now to FIG. 5, we see a flow diagram of the algorithm
executed by the second microprocessor 12 of FIG. 1. The algorithm
enters a loop at START 51. Block 52 inspects the facsimile modem 15
for an incoming call. If there is an incoming call, Block 55
answers the call and Block 56 communicates with the calling
computer to receive all of the set-up data, some of which is stored
in the first RAM 10 for the first microprocessor 7 and employed in
Blocks 43, 44, 46, 47 and 48 of the algorithm shown in FIG. 4, and
the rest of which is stored in the second RAM 14 for the second
microprocessor 12 and employed in blocks 54, 59 and 65 of the
algorithm in FIG. 5. The set-up data may include a phone number
employed in Block 65, an elapsed time trigger interval employed in
Block 54, a report format employed in Block 59, and thresholds and
calculation instructions used in Blocks 43, 44, 46, and 47 of FIG.
4. After receiving the set-up data from the calling computer, the
algorithm hangs up the phone in Block 57.
If the calling computer requests a report, or if no communication
can be established with the calling computer, block 56
automatically generates and sends a facsimile report. This permits
a user to trigger a report simply by calling the instrument,
waiting for it to answer, then hanging up. No risk of disclosing
confidential data to unauthorized users occurs, because any report
generated in response to a hang-up is always sent to the telephone
number stored in the set-up data RAM 14.
If no incoming call was detected in Block 52, Block 53 inspects the
trigger line 11 from the first microprocessor 7 which may have been
made active by Block 49 of FIG. 4. If the trigger line 11 is
active, Blocks 58 through 66 are executed and a facsimile report is
sent. If its is not active, Block 54 inspects the real-time
clock/calendar 9 of FIG. 1 and compares the elapsed time to an
interval value stored in the set-up data 14. If the interval has
elapsed, Block 54 causes Blocks 58 through 66 to be executed and a
facsimile report is sent. Block 54 allows the set-up data to
specify that the instrument should send a facsimile report once
each month, for example, whether or not any thresholds have been
exceeded. Alternatively, Block 54 can be set up to trigger a report
at particular hours each day or on particular days of each week or
month.
Blocks 58 through 66 prepare and send a facsimile report. Block 58
acquires the data that was accumulated in the first RAM 10 by
Blocks 42 and 45 of FIG. 4. Block 59 acquires the report format
from the set-up RAM 14. This report format may specify the format
and contents of a cover page, the format, content, and calculation
process for a textual summary of the accumulated data 10, and the
format, content, labelling, and calculation process for graphical
summaries of the accumulated data 10. Block 60 employs bit-mapped
font tables, line drawing algorithms, and other well-known
techniques to convert the report format from Block 59 and the
accumulated data from Block 58 into a bit-mapped image of the
report such as the one shown in FIG. 2. Due to memory limitations
in the second RAM 14, it may not be possible to construct a bit-map
of the entire report, so Block 60 restricts itself to construction
of a single line of the report. Blocks 62 and 61 then allow as much
of the report as will fit in memory to be constructed. Block 63
compresses the bit-map using any well-known algorithm such as
CCITT-3 before passing the data to a facsimile modem 15. Block 64
checks to see if the modem is already on-line to a facsimile
receiver. If it is not, Block 65 dials the number specified in the
set-up data 14 and establishes communication with a facsimile
receiver. If the set-up data specifies, Block 65 may also execute
well-known re-try algorithms or alternate-dial algorithms if it is
unable to establish communication. Once communication has been
established, Block 66 transmits the compressed bit-mapped image to
the facsimile receiver then deletes the bit-map from memory thus
clearing space for the next section of the report. Block 67
continues this loop until the report is complete, at which time
Block 57 hangs up the telephone connection and restores the test
loop beginning at Block 52.
Various modifications may be made to the preferred embodiment
without departing from the spirit and scope of the invention as
defined by the appended claims. Various allocation of the
processing requirements between one or more microprocessors may be
made.
* * * * *